My Imaginary Mary by Cynthia Hand

It’s aliiiiiiiive! The bestselling authors of My Lady Jane are back with the electric, poetic, and (almost) historical tale of the one and only Mary Shelley.

Mary may have inherited the brilliant mind of her late mother, Mary Wollstonecraft, but she lives a drab life above her father’s bookstore, waiting for an extraordinary idea that’ll inspire a work worthy of her parentage—and impress her rakishly handsome (and super-secret) beau, Percy Shelley.
Ada Lovelace knows a thing or two about superstar parents, what with her dad being Lord Byron, the most famous poet on Earth. But her passions lie far beyond the arts—in mechanical engineering, to be exact. Alas, no matter how precise Ada’s calculations, there’s always a man willing to claim her ingenious ideas as his own.
Pan, a.k.a. Practical Automaton Number One, is Ada’s greatest idea yet: a machine that will change the world, if only she can figure out how to make him truly autonomous . . . or how to make him work at all.
When fate connects our two masterminds, Mary and Ada learn that they are fae—magical people with the ability to make whatever they imagine become real. But when their dream team results in a living, breathing, thinking PAN, Mary and Ada find themselves hunted by a mad scientist who won’t stop until he finds out how they made a real boy out of spare parts.